In addition to targeting the right audience with the right marketing message at the right time, you need to get it out as far and wide as possible. But doing so can be expensive. Consider using smaller ads in a variety of publications rather than one big ad or co-advertise with another small business in the same ad space.
Coming up with an effective ad is not an easy but a necessary task. Review your ads yourself or ask someone else to do it for you. Analyze why they did not generate any interest then build your new ads with some changes, including changes in your approach. Implement the changes incrementally and track them so that you know how well they are doing.